Quantitation of reflux and outflow obstruction in patients with CVD and correlation with clinical severity

Chronic venous disease (CVD) is the result of venous reflux, obstruction or a combination of both. So far, attempts to correlate venous hemodynamic measurements with symptoms and signs of CVD have produced poor to moderate results, probably because of lack of methods to quantitate obstruction and combine measurements of reflux and obstruction. Our hypothesis is that the combination of quantitative measurements of (a) overall reflux (superficial and deep) and (b) overall outflow resistance i.e. including the collateral circulation would provide a hemodynamic index that should be related to the severity of the disease.

Twenty-five limbs with chronic venous disease and 1 limb from a healthy volunteer (VCSS 0-13) were studied. The clinical CEAP classification was C0 in one limb, C1 in 2 limbs, C2 in 10 limbs, C3 in 3 limbs, C4 in 1 limb, C5 in 6 limbs and C6 in 3 limbs. Air-plethysmography was used to measure reflux (VFI in mL/s) when the subject changed position from horizontal to standing. Subsequently, with the subject horizontal and the foot elevated 15 cm, simultaneous recordings of pressure and volume were made on release of a proximal thigh cuff inflated to 70 mmHg. Pressure change was recorded with a needle in the foot and volume change with air-plethysmography. Flow (Q in mL/min) was calculated at intervals of 0.1 seconds from tangents on the volume outflow curve. Outflow resistance (R) was calculated at 0.1 second intervals by dividing pressure by the corresponding flow (R=P/Q). R increased markedly at pressures lower than 25 mmHg due to decrease in vein cross-sectional area, so resistance at 25 mmHg (R25) was used in this study.

In a multivariable linear regression analysis with VCSS as the dependent variable, both VFI and R25 were independent predictors (P<0.001). Using the constant (0.595) and regression coefficients, the regression equation provided a Hemodynamic Index (HI) or estimated VCSS=0.595 + (VFI x 0.41) + (R25 x 98). Thus, HI could be calculated for every patient by substituting VFI and R25 in the equation. HI or calculated VCSS was linearly related to the observed VCSS (r=0.86).

The results indicate that the combination of quantitative measurements of reflux and outflow resistance provide a hemodynamic index which is linearly related to the VCSS. These findings need to be confirmed in larger series.